1. Field of the Invention
The present invention relates to electronic circuits, and more particularly to an electronic circuit arrangement for supplying a constant voltage supply to an operating circuit for a period of time after power to the operating circuit has been lost.
2. Background
Numerous electronic devices implement a shut-down procedure upon loss of power to the device. To execute the shut-down procedures, electrical circuits in the device must continue to receive power after the device has lost power.
By way of example, Telecommunications standard ITU 992.1 requires that a series of “Dying Gasp” messages be sent by the ADSL Customer Premises modem through the data connection to the Central Office modem upon loss of power. Therefore, an ADSL modem requires a source of uninterruptable power to maintain an existing ADSL modem connection for up to 50 milliseconds after input power is lost, in order to complete the transmission of “Dying Gasp” messages. There is no further need to maintain power to the modem once the “Dying Gasp” messages are sent.
Accordingly, there remains a need in the art for short-term uninterruptible power supplies for use with electronic devices.